On 12/10/2019 4:27 PM, Rafael J. Wysocki wrote:
On Tue, Dec 10, 2019 at 9:19 AM Tao Xu <tao3.xu@xxxxxxxxx> wrote:
On 12/10/2019 4:06 PM, Rafael J. Wysocki wrote:
On Tue, Dec 10, 2019 at 2:04 AM Tao Xu <tao3.xu@xxxxxxxxx> wrote:
On 12/9/2019 6:01 PM, Rafael J. Wysocki wrote:
On Mon, Dec 2, 2019 at 8:03 AM Tao Xu <tao3.xu@xxxxxxxxx> wrote:
In chapter 5.2.27.5, Table 5-147: Field "Cache Attributes" of
ACPI 6.3 spec: 0 is "None", 1 is "Direct Mapped", 2 is "Complex Cache
Indexing" for Cache Associativity; 0 is "None", 1 is "Write Back",
2 is "Write Through" for Write Policy.
Well, I'm not sure what the connection between the above statement,
which is correct AFAICS, and the changes made by the patch is.
Is that the *_OTHER symbol names are confusing or something deeper?
Because in include/acpi/actbl1.h:
#define ACPI_HMAT_CA_NONE (0)
ACPI_HMAT_CA_NONE is 0, but in include/linux/node.h:
enum cache_indexing {
NODE_CACHE_DIRECT_MAP,
NODE_CACHE_INDEXED,
NODE_CACHE_OTHER,
};
NODE_CACHE_OTHER is 2, and for otner enum:
case ACPI_HMAT_CA_DIRECT_MAPPED:
tcache->cache_attrs.indexing = NODE_CACHE_DIRECT_MAP;
break;
case ACPI_HMAT_CA_COMPLEX_CACHE_INDEXING:
tcache->cache_attrs.indexing = NODE_CACHE_INDEXED;
break;
in include/acpi/actbl1.h:
#define ACPI_HMAT_CA_DIRECT_MAPPED (1)
#define ACPI_HMAT_CA_COMPLEX_CACHE_INDEXING (2)
but in include/linux/node.h:
NODE_CACHE_DIRECT_MAP is 0, NODE_CACHE_INDEXED is 1. This is incorrect.
Why is it incorrect?
Sorry I paste the wrong pre-define.
This is the incorrect line:
case ACPI_HMAT_CA_DIRECT_MAPPED:
tcache->cache_attrs.indexing = NODE_CACHE_DIRECT_MAP;
ACPI_HMAT_CA_DIRECT_MAPPED is 1, NODE_CACHE_DIRECT_MAP is 0. That means
if HMAT table input 1 for cache_attrs.indexing, kernel store 0 in
cache_attrs.indexing. But in ACPI 6.3, 0 means "None". So for the whole
switch codes:
This is a mapping between the ACPI-defined values and the generic ones
defined in the kernel. There is not rule I know of by which they must
be the same numbers. Or is there such a rule which I'm missing?
As long as cache_attrs.indexing is used consistently going forward,
the difference between the ACPI-defined numbers and its values
shouldn't matter, should it?
Yes, it will not influence the ACPI HMAT tables. Only influence is the
sysfs, as in
https://www.kernel.org/doc/html/latest/admin-guide/mm/numaperf.html:
# tree sys/devices/system/node/node0/memory_side_cache/
/sys/devices/system/node/node0/memory_side_cache/
|-- index1
| |-- indexing
| |-- line_size
| |-- size
| `-- write_policy
indexing is parsed in this file, so it can be read by user-space.
Although now there is no user-space tool use this information to do some
thing. But I am wondering if it is used in the future, someone use it to
show the memory side cache information to user or use it to do
performance turning.
